Resonant sound signal device



y 18, 1954 H. H. HALL ET AL RESONANT SOUND SIGNAL DEVICE Filed Sept. 10;, 1951 INVENTORS: Hawgy H Hall and Patented May 18, 1954 NEED ATENT OFFICE RESONANCE SOUND SIGNAL DEVICE Application September 10, 1951, Serial No. 245,882

4 Claims.

This invention relates to improvements in signal devices of fluid-pressure operated type, and has reference more particularly to a resonant signal device characterized by a markedly improved operating efiiciency and by a stable signal output at any preselected frequency. Although the presently improved device is capable of a wide variety of applications as a signalling and warning medium, it is especially suitable for use on self-propelled railway vehicles such as steam and diesel-electric locomotives, to provide a penetrating warning signal having a pleasing musical tone at a selected frequency which may be in the range of maximum sensitivity of the human ear.

As will appear more fully hereinafter, the signal device forming the subject of this invention,

comprised of a whistle and a sound amplifying horn in close-coupled assembly, wherein the whistle portion is formed and constructed to provide a closed resonant chamber about the input end portion of the horn, and orifice means constituted by an annular series of ports opening to the chamber for admitting a signal energiz- 111g fluid under pressure, as steam or compressed air. Further, the annular end margin at the terminal of the input end of the horn, is in substantial registry with the annular series of ports and spaced therefrom to a predetermined extent, such that the signal energizing fluid under pressure issuing through the ports will impinge upon the horn end margin and be divided thereby between the resonant chamber and the input passage of the horn. In such an arrangement the cavity has a resonant function supplementing that of the horn, so that through proper selection of the dimensions of resonant chamber, chamber opening, and the sound coupling and amplifying horn, the signal device may be thereby conditioned to produce a stable signal at any desired frequency.

objectively stated, the principal aim of the present invention is to provide a highly efficient resonant signal device of the character and relatively simple construction generally described hereinabove, which does not require any moving parts, and which will produce a stable and eiTective signal tuned to any desired frequency.

Another object is to provide a signal device of the character indicated, in which the whistle portion of the device has its fluid-pressure admission orifice means located inside the whistle housing, and in which the amplifying horn element thereof is close-coupled to the whistle such that the opening to the whistle chamber or resonant cavity is substantially at the input throat of the horn, thereby attaining an efiicient and highly efiective coupling of the entire acoustical output of the Whistle to the atmosphere.

A further object resides in the provision of a signal device of the character described, in which the closed resonant chamber of the whistle and the horn are so formed and related in operative assembly, that each functions as a tuned resonator, with the result that the acoustical energy of the device will be radiated within a narrow frequency band. Consequently, in adaptation of the signal device to locomotive use the musical tone produced by the device may be readily distinguished at great distances, from surrounding masking noises.

These and other objects and advantages of the invention will appear readily from the following description of a presently preferred embodiment thereof illustrated in the accompanying drawing, wherein:

Fig. 1 illustrates the presently improved signal device, the view showing the whistle portion thereof and the input section of the horn in longitudinal sectional elevation.

Fig. 2 is a transverse sectional elevation of the device, as taken along line 22 in Fig. 1.

Fig. 3 is a further transverse sectional elevation, taken along line 33 in Fig. 1.

Referring to the drawing by appropriate char acters of reference, the signal device is comprised of a whistle designated generally by the numeral 59, and an amplifying horn H relative- 1y close-coupled to the whistle. The whistle is here constituted by 2. preferably cylindrical housing l2 having an integral end wall it and an opposite end wall I 5 provided as a separate disclike element detachably mounted in the recessed end portion 16 of the housing, in marginal abutment with the internal shoulder 38.

Wall 15 is formed to-provide a plurality of relatively small orifices or ports l9 opening through the wall and arranged in an annular series as shown more particularly in Fig. 2, with the ports preferably equally spaced in the series. Externally on the wall I5 is a circular extension or boss 20 threaded at its outer end to receive a conduit nipple or coupling member 22 for a supply conduit (not shown) leading from a suitable source of signal energizing fluid, as steam or compressed air. The energizing fluid received in the coupling chamber 23, passes therefrom through the ports l9 into the whistle casing I2.

The horn i i has its outwardly flaring delivery end portion 24 disposed outwardly beyond the end wall [4 of the whistle housing I2, while its substantially tubular input end portion 26 projects through an opening 21 in the end wall it and centrally in the housing [2 toward and terminating in relatively closely spaced relation to the orifices [9. Thus the input end portion 26 of the horn extending centrally in the housing, cooperates with the latter to form an annular resonant cavity or chamber 28 open only at the annular entrance throat or opening 30 which is in the plane of the terminal margin 3! of the horn. Moreover, the annular terminal end 34 of the horn input end portion is substantially in registry with the annular series of orifices l9 such that the signal energizing fluid issuing through the orifices, will impinge upon the horn end margin SI and be divided thereby, between the annular opening 30 to the resonant whistle chamber or cavity 28 and the throat 32 of the horn input passage 33. The stream-splitting action of the end margin 3! may be very considerably enhanced by tapering or bevelling it as shown, such that the margin presents a sharp or knife-like annular edge 34 to the impinging stream.

The horn II is retained in proper assembly position relative to the whistle housing, as by a press-fit of its tubular end portion 26 in the housing end wall opening 21, and by struts 35 extending radially in the whistle chamber between the tubular portion of the horn and the wall of the housing l2. Moreover, to facilitate mounting of the assembled signal device in operative position on a support such as the top portion of a diesel-electric locomotive cab, suitable feet or bracket means (not shown) may be provided on the whistle housing 12. Preferably also, the housing !2 may be provided with one or more drain holes 40 located to facilitate removal of any moisture tending to collect in the housing.

It is to be noted here that the several parts of the whistle structure, as Well as the horn, are formed of suitable rigid material, preferably metallic material of corrosion-resistant charac ter. vided of non-metallic or plastic materials, while the remaining parts including at least the terminal input end of the horn providing the stream splitting edge 34, are formed of corrosionresistant metal.

It should be fully apparent now from the foregoing description of the presently improved signal device, that the device provides a whistle housing and sound amplifying horn in operative assembly, such as to form a resonant cavity or chamber about the input section of the horn and closed but for a single annular opening or entrance throat wholly within the housing and surrounding the entrance throat of the horn, with admission of signal energizing fluid divided by the horn margin between the said entrance throats. This relationship of the horn and whistle has been found to produce a most efiective and highly efficient coupling of the sound wave energy of the whistle to the atmosphere. Moreover, in consequence of the arrangement described, the horn functions advantageously as a resonator supplemented by the resonant function of the whistle cavity. Accordingly, by proper selection as to the effective length of the horn, the capacity or volume of the whistle cavity or resonant chamber and area of its entrance throat, and the relationship of the fluid admission orifice means and the tapered terminal edge of the horn, the signal device may be conditioned to If desired, certain of the parts may be rohave desired resonant frequency and sound output characteristics. It is to be noted further, that the resonant cavity is not limited to the circular form illustrated, but may be of any other shape or configuration, as of square, rectangular, hexagonal or other section, so long as the shape thereof provides the required cavity volume and area of its entrance throat.

In one exemplary embodiment of a signal device constructed in accordance with the present invention, the desired resonant frequency of about 550 cycles per second was obtained through provision of a horn having an efiective length of 24 inches, such length being that corresponding to the distance between the entrance throat of the horn and that zone of its flared output end which has a diameter about twice the diameter of the entrance throat. The resonant cavity coupled to the horn, as the cavity 28 in Fig. l, was formed to have a volume of approximately 44 cubic inches, while the area of the annular opening to the cavity, as the opening 30, was approximately 0.95 square inch. The resonant cavity having the above dimensional factors, greatly reinforced the signal tone and markedly improved the efficiency and sound output of the signal device.

Considering further the foregoing exemplary embodiment, reducing the effective length of the horn by half, as to 12 inches, will result in increasing the resonant frequency thereof to about 1109 cycles per second. In such instance, the volume of the resonant cavity required for efficient operation of the signal device, will be about one-half of that necessary for the 24 inch horn, or about 22 cubic inches, while keeping the area of the cavity throat at the same value, as 0.95 square inch. Conversely, a horn of double the given effective length, as 48 inches, will have a resonant frequency of about 275 cycles per second, and in this case, the resonant cavity should have a volume of approximately 88 cubic inches with the same throat area of 0.95 square inch.

importantly to the operating stability of the improved signal device and to the conservation of signal energizing fluid, the fluid employed, as steam or compressed air, is admitted through an annular series of small ports or openings, as [9, related in spaced opposition to the horn throat margin as hereinbefore described. Forming the fluid orifice by a multiplicity of small openings in the annular arrangement disclosed, rather than by a single annular slot opening, results in a more stable jet discharge into the signal device, with a material reduction in the rate of consumption of the energizing fiuid. As an example of the size and number of the jet ports, in the exemplary embodiment referred to hereinbefore a total of 24 holes were employed each having a diameter of a; of an inch.

The signal device according to this invention, is characterized not only by the several advantages 'hereinabove referred to, but very importantly herein by a relatively high operating efficiency, exceeding very appreciably the operating efficiencies of heretofore prevailing horns and whistles of fluid pressure energized type. Such high efficiency is here attained in great art by reason of the closed resonant whistle chamber about the input section of the horn, since this chamber affords increased fluid turbulence in the region of the horn throat opposite the whistle orifice, and importantly constrains the sound generated to passage through the horn.

Having now described and illustrated a presw ently preferred embodiment of the invention, it is to be understood that modifications may be made in the structure and arrangement of parts thereof without departing from the spirit and full intended scope of the invention.

What is claimed is:

i. In a signal device, a housing having end walls and providing ports in one end wall thereof for the admission of signal energizing fluid under pressure, said ports being arranged in a circular series, and a sound transmitting and amplifying horn having a substantially tubular input end portion extending in said housing through the other end wall thereof and terminating in an open input end disposed in relatively closely spaced opposition to said ports, the circular margin of said tubular end portion at said open end being disposed substantially in alignment with said circular series of ports.

2. In a signal device, means providing a whistle chamber having an annular series of orifices opening to the chamber for the admission of signal energizing fluid under pressure, and a sound amplifying horn providing a generally tubular input end portion extending in said chamber toward said orifices and defining in said chamber a resonant cavity about the tubular end portion, the annular terminal margin of said tubular end portion providing a sharp edge in substantial registry with said annular series of orifices, serving to divide the fluid stream issuing through said orifices, between said resonant cavity and the interior of the horn input end portion.

3. In a fluid-pressure operated signal device, a sound amplifying horn having a generally tubular input end portion terminating at its open input end, in a tapered margin providing a sharp annular edge, means cooperating with said tubular end portion to provide a whistle cavity about said portion and communicating with the open input end of the latter, said means including a wall spaced from the open input end of the horn and having an annular series of ports opening therethrough in substantial registry with said sharp annular edge of the horn input end, said ports being provided for the admission of signal energizing fluid under pressure, the fluid issuing through the ports impinging on said sharp annular edge and being divided thereby between said whistle cavity and the open input end of the horn.

4. In a fluid-pressure operated signal device, a housing having end walls and providing a plurality of ports opening through one end wall thereof, said ports being arranged in an annular series and being provided for the admission of signal energizing fluid under pressure into the housing, a horn having a generally tubular input end portion projecting through the other end wall of the housing and extending centrally in the housing toward said annular series of ports, said input end portion of the horn terminating in a sharp annular margin in spaced registry with the annular series of ports, and said housing and input end portion of the horn cooperating to form a resonant cavity about the latter and a cavity entrance throat adjacent said terminal margin of the horn input portion.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 291,5 l8 Swan Jan. 8, 1884 1,2 8,058 Sleeper Oct. 2, 1917 1,698,296 Brandegger Jan. 8, 1929 FOREIGN PATENTS Number Country Date 517,072 France Apr. 29, 1921 525,308 France June 1, 1921 

